Agriculture often is considered to be a contributor of soluble reactive phosphorus (SRP) and nitrate-N (NO3-N) to surface waters. This research analyzed SRP and NO3-N concentrations in groundwater and in a creek fed by groundwater on a valley dairy farm in the Cannonsville basin of the New York City watershed.
Water-table depth and concentrations of SRP, NO3-N, dissolved organic carbon (DOC), and dissolved oxygen were measured at regular intervals over a three-year period. A multivariate mixed model analysis of variance indicated that the SRP and NO3-N concentrations were controlled primarily by environmental variables, including precipitation and water table depth; source variables, including manure applied and crop type; and chemical variables, including DOC and dissolved oxygen concentrations in groundwater.
The highest groundwater concentrations of NO3-N and SRP were found at the shallowest water-table depths, which has implications for agricultural nutrient management in areas with shallow groundwater.
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